Context dependency of rewards and services in an Indian ant–plant interaction: southern sites favour the mutualism between plants and ants

Abstract

Borges (2014). Context dependency of rewards and services in an Indian ant-plant interaction: southern sites favour the mutualism between plants and ants .Abstract: Protection-based ant-plant mutualisms may vary in strength due to differences in ant rewards, abundance of protective ants and herbivory pressure. We investigated geographical and temporal variation in host plant traits and herbivory pressure at five sites spanning the distribution range of the myrmecophyte Humboldtia brunonis (Fabaceae) in the Indian Western Ghats. Southern sites had, on average, 2.4 times greater abundance of domatia-bearing individuals, 1.6 times greater extrafloral nectary numbers per leaf, 1.2 times larger extrafloral nectary sizes, 2.2 times greater extrafloral nectar (EFN) volumes and a two-fold increase in total amino acid and total sugar concentrations in EFN compared with northern sites. A strong protection-based mutualism with ants occurred at only one southern site where herbivory was highest, suggesting that investments in attracting ants correlate with anti-herbivore benefits gained from the presence of protective ants. Our results confirm a temporally stable north-south gradient in myrmecophytic traits in this ant-plant as several of these traits were re-sampled after a 5-y interval. However, the chemical composition of EFN varied at both spatial and short-term temporal scales suggesting that only repeated measurements of rewards such as EFN can reveal the real spectrum of trait variation in an ant-plant mutualistic system.

Three new species of nematodes from the syconia of Ficus racemosa in southern India

“…The morphs (δ, ε) with simple, tube-like buccal cavities devoid of effective armature seem to compete for a temporary bacterial food source whereas the predatory morphs (α, γ) emerge next coinciding with the proliferation of wasp-transmitted nematodes in the syconium. Development of greater number of morphs might be due to the high climatic and seasonal variation which is observed in southern India (Gadgil & Joshi, 1983;Gunnel 1997;Peel et al, 2007;Shenoy & Borges, 2010;Chanam et al, 2014). We observed sex specific stomatal morphs (β = adult female only) versus (γ,δ, ε = adult males only) which requires further validation through a study similar to that reported in Susoy et al (2016) with Pristionchus sycomori where different early and late interfloral (phase C) figs were examined and large numbers of Pristionchus were sexed and assessed for stomatal morphotype.…”

Foliar Extrafloral Nectar of Humboldtia brunonis (Fabaceae), a Paleotropic Ant‐plant, is Richer than Phloem Sap and More Attractive than Honeydew

“…, Chanam et al . ). Domatia‐bearing plants are rewarded by nitrogen absorbed from domatia that are occupied even by non‐protective EFN‐consuming ants (Chanam et al .…”

“…, Chanam et al . ) and within the context of a trophic mutualism with ants (Chanam et al . ) but also to distract the ants from tending Hemiptera.…”

Phenotypic plasticity in size of ant-domatia

“…Humboldtia brunonis is one of the rare ant-plant species in which both domatia-bearing and domatia-free individuals occur 14 . In this species, the proportion of domatia-bearing plants varies geographically and is higher in sites with stronger herbivore pressure 15 . Ants that live on plants sometimes cut floral buds, which increases vegetative growth, and eventually benefits the ant colony.…”